The present invention relates generally to a method and apparatus for extracting a molded product from an injection molding die. More particularly, the present invention relates to a method and apparatus for extracting from an injection molding die a slidable shutter adapted to be attached to a cartridge Case in which a disc-shaped recording medium is received.
In recent years, disc-shaped recording media such as magnetic discs, optical discs, photomagnetic discs and the like have been increasingly used owing to their advantageous properties, e.g., simple and easy handling and large data storage capacity per unit volume of disc.
A 3.5 inch micro floppy disc as shown in FIG. 5 is a typical example of a disc cartridge employable as a disc-shaped recording medium. This micro-floppy disc 1 is constructed such that a magnetic disc 5 is rotatably received in the hollow space defined between upper and lower rectangular shell halves 2 and 3 injection-molded of acrylonitrile-butadiene-styrene copolymer resin or the like. The magnetic disc 5 is prepared in the form of a magnetic recording medium having a magnetic layer uniformly formed on the surface of a circular high-molecular film base, and a ring-shaped center plate 4 is secured to a circular opening formed at the central part of the magnetic disc 5. In addition, a circular opening 7 is formed at the central part of the lower shell half 3 of the micro-floppy disc 1 so as, to allow a motor shaft to be inserted into a substantially square motor shaft insert hole 6 formed at the central part of the center plate 4.
Additionally, magnetic head insertion openings 8 are formed on the upper and lower shell halves 2 and 3 so as to allow a magnetic head and a head pad to be received in the foregoing openings 8 in order to electromagnetically write data to or read data from the magnetic disc 5.
To prevent dust or similar foreign material from entering the micro-floppy disc 1 via the magnetic head insertion openings 8 and then adhering to the disc, the micro-floppy disc 1 is provided with a slide-type shutter 9 for opening and closing the magnetic head insert openings 8.
The shutter 9 has hitherto been made by bending a metal sheet such as a stainless steel sheet or the like to obtain a U-shaped cross-sectional contour.
The shutter 9 can slidably be displaced in the direction of opening/closing of the magnetic head insert openings 8 with the aid of projections extending inward of the inner wall of the shutter 9 in the vicinity of the bottom of the latter and a guide groove adapted to receive the projections. The guide groove extends parallel to the side edge on the front surface of the lower shell half 3. In other words, the shutter 9 can slidably be displaced within a slidable movement region 11 along the side wall surfaces of the micro-floppy disc 1, which region includes the periphery of each magnetic head insertion opening 8.
In addition, openings 10 are formed on the shutter 9 positionally aligned with the magnetic head insertion openings 8 so as to allow the magnetic disc 5 to be exposed to the outside therethrough when the micro-floppy disc 1 is in the operative state. On the other hand, the magnetic head insertion openings 8 are closed by the shutter 9, causing the magnetic disc 5 to be covered with the shutter 9 as illustrated by phantom lines in FIG. 5, when the micro-floppy disc is in the inoperative (storage) state.
Recently, various proposals have been made to replace the conventional metal shutter with a less expensive shutter molded of a synthetic resin. See, for example, Japanese Patent Laid-Open Publications Nos. 60-231985 and 64-70981. In consideration of the function of the shutter, a crystalline plastic material having a self-lubricating property, such as polyacetal resin, has generally been used as the synthetic resin for the shutter. With a crystalline plastic material, however, it is required that the molding die in which the material is injected be heated to a high temperature sufficient to promote growth of crystals (normally about 70.degree. C. to 90.degree. C.). As a result, the molded product must be extracted from the injection molding die also at an elevated temperature, typically about 80.degree. C. to 100.degree. C.
To extract the molded product from the mold and pass it to a subsequent production processing station, a chucking (extraction) apparatus as disclosed in, e.g., Japanese Utility Model Laid-Open Publications Nos. 57-4310 and 59-129517 has hitherto been used. Specifically, such a chucking apparatus is constructed such that a pair of chuck members, which are opened and closed by cylinders, squeeze the molded product in such a manner as to clamp it from opposite sides with chucking surfaces. The molded product is then extracted from the injection molding die.
However, when a shutter is molded of a synthetic resin, as already discussed, the molded product must be extracted from the injection molding die at a high temperature. This molded product has a very small thickness ranging from about 0.2 mm to 0.5 mm. For this reason, when an extracting apparatus of the type described above is employed for the purpose of extracting the molded product from the injection molding die, there arises a problem in that the molded product can be readily deformed by only a relatively small exterior force (chucking force) imparted by the extracting apparatus. In addition, since the shutter, i.e., molded product, is deeply received in the injection molding die, when it is clamped from the opposite sides in the direction at a right angle relative to the direction of extraction at positions offset from predetermined positions during the extracting operation, there arises another problem in that an abnormally high extracting force acts on the molded product.
Further, when a U-shaped shutter 50 (molded product) having a very small thickness is held by chucking surfaces 51 from the opposite sides in the clamped state, sometimes the shutter 50 is held in an inclined state such that only one side wall of the shutter 50 contacts the chucking surface 51, causing the rear surface 50a (U-shaped bent joint portion) of the shutter 50 to be convexly deformed, as illustrated by phantom lines in FIG. 6. Once such convex deformation occurs, precise gripping of the shutter 50 is not assured, and, moreover, correct transference of the shutter 50 to a subsequent processing stage can be achieved only with much difficulty.
Since each chucking surface 51 is generally lined with an elastic material 52, left- and right-hand corner portions 50b of the rear surface 50a forcibly encroach on both elastic materials 52, resulting in small recesses 53 being formed thereon. The presence of these recesses 53 sometimes leads to a part of the shutter 50 located directly below each corner portion 50b being concavely deformed.
To avoid deforming the shutter 50 by the chucking surfaces, it might be considered to reduce the magnitude of chucking force. However, if the chucking force is weakened, the reliability for holding the shutter 50 in the clamped state is reduced. For this reason, it is very difficult to properly adjust the magnitude of the chucking force.
In another conventional extracting apparatus of the foregoing type, a suction pad is brought in close contact with the rear surface of the shutter from above so that the shutter is extracted from the injection molding die while maintaining the desired orientation of the shutter. However, when the apparatus is provided with a suction pad, since the rear surface of the shutter has a very small thickness of about 3.6 mm, it is necessary that the position of the suction pad be precisely controlled in order to assure that the suction pad can provide a sufficiently high suction force. For this purpose, as shown in FIG. 7, after a shutter 50 is raised a predetermined height above the injection molding die by actuating an ejection pin 61, the shutter 50 is brought into close contact with a suction pad 63 disposed at a certain deep position in a guide 64 having inclined guide surfaces 65 formed thereon to guide the raising movement of both side surfaces of the shutter 50.
However, since the shutter 50 is still at an elevated temperature and hence is still quite soft, an abnormal force can readily be imparted to the shutter 50 when the rear surface 50a of the shutter is inserted into the guide 64 toward the suction pad 63 along the inclined guide surfaces 65, resulting in the position of the guide 64 being largely dislocated. In an extreme case, the ejection pin 61 can be damaged or broken by the guide 64.
Japanese Utility Model Laid-Open Publication No. 57-129517 illustrates a chucking apparatus constructed such that a molded product is clamped from opposite sides by a pair of chuck members each including a suction pad on one side thereof. With the chucking apparatus constructed in the above-described manner, a vacuum switch is provided to detect whether or not the molded product is clamped by the chuck members via the suction pads. In this case, the molded product is held by the chuck members, and each suction pad serves merely as detecting means. Since each suction pad is fitted into a recess formed on the chucking surface of the corresponding chuck member, when it is used as holding means, it cannot make soft contact with the molded product because it does not project from the open end of the recess formed on the chuck member.
In case that the molded product is held merely by the suction pad disposed on one side, there is a possibility that the molded product is held in an inclined state. In addition, in case that the molded product is held directly by the forward ends of piston rods in pneumatic cylinders, it is difficult as a practical matter to finely adjust the magnitude of holding force applied by the pneumatic cylinders. For this reason, employment of the pneumatic cylinders in the above manner is not suitable for holding a soft molded product such as a shutter or the like. In addition, employment of two pneumatic cylinders for holding a single molded product is not acceptable for economical reasons.
Further, Japanese Utility Model Laid-Open Publication No. 57-4310 describes a chucking apparatus constructed such that a molded product molded of a synthetic resin is held by a grasping member including contact pieces. With this construction, the grasping member, operatively connected to a cylinder unit, serves to grasp a molded product such as scissors by a turning movement of the grasping member about a pin. However, it is very difficult to finely adjust the magnitude of the force for clamping the molded product with the aid of the grasping member connected directly to the cylinder unit. Also in this case, the grasping member grasps a member harder than the shutter. Thus, the grasping member cannot be employed as a holding member for holding a soft molded product such as a shutter formed by a sheet material.